Current techniques for providing autonomous motion down a lumen generally involve a relatively complicated mechanism with multiple moving parts, which restricts miniaturization because of current technological limitations. Moreover those techniques often require sequential controlled actuations, thus complicating their operation.
Furthermore most methods commonly used cannot operate in confined spaces such as relatively small pipes, or in environments other than those predetermined for the device. Due to the complexity, the multiplicity of moving parts, the possible need of actuators, and control circuits, sensors and internal power sources, prior art mechanisms suffer size limitations, have complex assemblies and relatively high cost, specifically in narrow environments like pipes where miniaturization is essential. More specifically for medical applications, where there is demand for biocompatible miniature systems with a minimal number of moving parts (for medical safety reasons) prior art mechanisms are generally far from optimal.
Hence, there is a need for an autonomous miniature moving mechanism which should be simple, composed of a minimal number of moving parts and which performs well in different environments.
Locomotion inspired by the peristaltic motion of Annelids, and especially of earthworms, has suggested the use of friction between oscillating microstructures and the wall of a lumen or the surface to be traversed. Such devices offer promise for a simple robotic autonomous crawling device.
The paper entitled “Development of a biomimetic miniature robotic crawler” published in Autonomous Robots Journal Vol 21(2) pg. 155-163, describes the development of segmented artificial crawlers endowed with passive hook-shaped frictional microstructures, using a Shape-Memory-Alloy spring which causing its torso to alternately shrink and expand with large amplitude and at low frequencies, thereby, causing locomotion. The hooks provide the anisotropic friction necessary for the progress of the device.
In the paper “In pipe bristled micromachine” published in Advanced Motion Control, 2002, Pg. 599-603, the micromachine locomotion principle is based on a directional friction force between the tips of inclined oscillating bristles and the pipe wall. A small amplitude and high frequency piezoactuator is used in the device torso.
In both of these systems the friction-members limits the contact surface geometry i.e. if applied as an in-pipe moving robot, since no adjusting mechanism is embodied, the diameter range in which such a robot can be applied is narrow. Furthermore, the motion is achieved by changing the distance between two or more anchoring bristles by the use of a size varying actuator such as a Shape-Memory-Alloy or Piezoelectric actuator.
U.S. Pat. No. 2,917,762 for “Apparatus for Traveling through Pipes” to C. P. Xenis, describes an apparatus for in-pipe travel comprised of inclined stiff fibers arranged in a cylindrical manner, having a diameter slightly in excess of the inner diameter of the conduit, and which advances due to vibrations. As described, an inclination angle of about 15 degrees between the fibers and the normal to the longitudinal axis of the apparatus will generate suitable anisotropic friction with the pipe's inner surface while in contact. However the fiber's stiffness and the friction which is induced solely at the tips of the fibers limit the pipe diameter range to which such an apparatus may be applied. In addition this apparatus is limited to uses within a pipe.
U.S. Pat. No. 3,885,356 for “Vibratory Conveyor and Abrader” to J. W. Armstrong describes a conveyer belt system using a vibrating pile material having resilient fibers inclined towards the direction of feed, and vibrated in a direction close to that of the fibers, in order to move objects placed thereupon. This patent describes specific use only of the tips of the vibrating fibers for supporting the load and for providing the motion thereto.
U.S. Pat. No. 5,575,378 for “Transfer Method and Apparatus Therefor” to A. J. Billington et al, describes another vibrating fiber conveyer system, which, instead of fibers, uses a multiplicity of extremely fine and relatively short flexible fibers packed at an ultra high density pile to provide a cushion element for moving a load placed on the fibers. The fibers may also be positioned on an object to move it relative to a base. Use of this fiber construction avoids damage to fragile objects transported by the conveyor.
U.S. Pat. No. 5,770,913 for “Actuators, motors and wheel-less autonomous robots using vibratory transducer drivers” to J. V. Mizzi describes a device providing one of an actuator, motor and a wheel-less autonomous robot using vibratory transducer drivers. The vibratory transducer driver is connected to a reciprocating element, driven reciprocally by the vibration driver. A friction surface is provided for translating reciprocating movement of the reciprocating element into motion. A driven member is moved by contact with the friction surface. This patent suggested a “Fibre-Tran” material supplied by the 3M Company as being a good material for use in the described invention. This material is based on anisotropic friction using the tips of inclined fibers.
Bristle tip-based oscillational crawlers may be limited to specific spatial situations such as pipes having a predetermined diameter and with only small variations in diameter, and moreover to specifically sequential or controlled oscillations. There is a need in the art for an autonomous robot using the vibrational fiber principle, which overcomes some of the disadvantages of previous such devices, and which can comply to a wide and varying range of pipes diameters, and which comprises a minimal number of moving parts, is low in cost and easy to manufacture.
The disclosures of each of the publications mentioned in this section and in other sections of the specification are hereby incorporated by reference, each in its entirety.